Cemented carbides possess a unique combination of hardness, strength and wear resistance. Accordingly, they are used extensively in industrial applications such as cutting tools, drawing dies and wear parts. Cemented carbides generally comprise carbide particles such as tungsten carbide, vanadium carbide, titanium carbide, tantalum carbide, molybdenum carbide, zirconium carbide, niobium carbide and/or chromium carbide. These carbide particles are bonded together by means of a metal such as cobalt, nickel, iron and alloys thereof. The bonding metal is typically in the range 3 to 40 weight percentage. Parts are generally produced by sintering the cemented carbide at temperatures of the order 1400° C. and above to produce full density porous free bodies.
Cubic boron nitride (cBN) is a superhard material surpassed only by diamond in hardness and is widely used in applications such as machining tools, e.g. grinding wheels, cutting tools etc. cBN is created under conditions of elevated temperature and pressure and the material is crystallographically stable at temperatures below 1400° C. Cemented carbide-cBN composites consisting of cBN particles dispersed in a cemented carbide matrix are previously known. Generally these composites are manufactured using high pressure sintering techniques to avoid formation of the low-hardness hexagonal polymorph of boron nitride (hBN). However, manufacturing routes involving such sintering techniques are expensive which has resulted in attempts to develop less expensive techniques.
EP 0 774 527 discloses manufacturing of WC-Co-cBN composites using direct resistance heating and pressurized sintering. “Making hardmetal even harder with dispersed CBN”, Metal Powder Report, Vol. 62, Issue 6, June 2007, p. 14-17, discloses an alternative direct resistance heating technique, Field Assisted Sintering Technology. The equipments used in such production methods, however, are suitable only for small batch volumes resulting in high production costs.
EP 0 256 829 discloses an abrasive and wear resistant material of cemented carbide containing cubic boron nitride and the manufacture thereof. However, the disclosed methods are still comparatively expensive or cannot provide the desired properties of a sintered composite body.
It is thus clear that there is still a need for a suitable production method for providing a sintered composite body comprising cubic boron nitride particles dispersed in a cemented carbide matrix.